The invention relates to a driving device for moving a tailgate.
Such a driving device for moving a tailgate has a permanent magnet brake that comprises a stationary portion, a first braking element, which is rotatable relative to the stationary portion about a rotational axis, and a second braking element, which is arranged in a rotationally fixed manner on the stationary portion. The first braking element and the second braking element are mutually axially offset along the rotational axis and cooperate in order to generate a braking force.
In a permanent magnet brake of this kind, as is known, for instance, from EP 0 693 633 A2, braking elements frictionally interact, wherein the friction force is magnetically influenced. In the permanent magnet brake of EP 0 693 633 A2, for instance, a permanent magnet, which acts on a braking element in the form of a pressure plate and by means of said pressure plate produces a pressure on a stack of friction elements, is provided. In addition to the permanent magnets, an electromagnet, which can be energized to switch the braking force on or off, is provided.
A drive for moving a vehicle part is also known from FR 2 818 304. The drive has a braking device for holding the vehicle part in a set position.
In a driving device known from DE 10 2005 030 053 A1, for pivoting a flap arranged on a body of a vehicle, there is provided a braking device, in which a brake disk acted on with braking effect by a braking element is arranged on a shaft.
From EP 1 534 971 B1, a magnetic brake actuated spring clutch, in which a magnet is arranged opposite to a rotor disk, is known. In the braking device which is described there, a braking force is produced by the induction of eddy currents.
Moreover, so-called wrap spring brakes, which use a wrap spring arranged in a brake pot, are known from the prior art. Upon the transmission of a drive-side force, the wrap spring is subjected to load for the release of a system comprising the brake pot, so that a drive shaft can be driven without great braking effect of the wrap spring. By contrast, when an output-side force is applied to the drive shaft, the wrap spring is subjected to load in the direction of its system comprising the brake pot, so that the drive shaft is braked and the output-side force is dissipated without this resulting in a movement of the drive shaft.
Traditional braking devices of this type are complex and have a considerable installation space requirement. Moreover, braking devices which utilize friction for the braking are susceptible to wear and, in some circumstances, sensitive to temperature.